The prior art is replete with helicopter designs and flight control systems for helicopters. A helicopter employs rotating blades that generate upward thrust that lifts the helicopter above the ground. FIG. 1 is a perspective view of a section of a helicopter 100, including two blades 102, an upper control mechanism 104, and two pitch link assemblies 106. In operation, upper control mechanism 104 (which rotates along with blades 102) actuates pitch link assemblies 106 to adjust the pitch of blades 102. In this regard, upper control mechanism 104 generally raises or lowers pitch link assemblies 106 to cause blades 102 to rotate about their respective longitudinal axes. The arrows 108 in FIG. 1 indicate the rotation of blades 102 about their longitudinal axes.
The pitch links of most helicopters include length adjusters that are centrally located between the ends of the pitch links. These length adjusters can be manipulated to ensure that all of the pitch links on the helicopter are of equal length, which results in proper in-flight operation, reduces vibrations, and enhances rotor performance. Some prior art helicopters include shields, guards, covers, or other equipment that protect the upper control mechanism from rain, snow, and other weather elements. FIG. 2 is a schematic partial cross sectional view of a prior art helicopter 200 having an upper control mechanism 202, a pitch link assembly 204, a canopy 206, and a protective boot 208; FIG. 3 is a top view of a portion of helicopter 200, showing only one blade 209 attached to the rotor. As shown in FIG. 3, helicopter 200 accommodates three blades and three respective pitch link assemblies 204 protruding through canopy 206. Canopy 206 is a rigid cover that extends over upper control mechanism 202, thus protecting upper control mechanism 202 from the elements. Canopy 206 includes holes formed therein; pitch link assembly 204 protrudes through one of these holes. Protective boot 208 encircles pitch link assembly 204 and spans the space between pitch link assembly 204 and canopy 206. In other words, protective boot 208 fills the gap created by the hole that receives the pitch link assembly 204.
Protective boot 208 is formed from a flexible material that enables upper control mechanism 202 to raise and lower pitch link assembly 204 without breaking the weather “seal.” In FIG. 2, protective boot 208 has a lower section 210 that resembles an accordion and an upper section 212 that resembles a sleeve. Lower section 210 is secured to the center of pitch link assembly 204 using string or laces 214, while upper section 212 is secured near the upper end of pitch link assembly 204 using string or laces 216. These laces 216 are concentrated about the upper end of the tube-shaped portion of protective boot 208. As depicted in FIG. 2, upper section 212 of protective boot 208 covers most of the portion of pitch link assembly 204 located above canopy 206.
Pitch link assembly 204 includes an adjustment mechanism 218 that is located under canopy 206 and, consequently, under protective boot 208. Adjustment mechanism 218 is rotated (using a wrench or other tool) in one direction to lengthen pitch link assembly 204, and is rotated in the opposite direction to shorten pitch link assembly 204. To adjust the length of pitch link assembly 204, protective boot 208 must be untied, removed, or disassembled to provide access to the hole formed in canopy 206. When upper control mechanism 202 is in the neutral position (as shown in FIG. 2), however, adjustment mechanism 218 is difficult to access from above canopy 206. Upper control mechanism 202 can be positioned such that adjustment mechanism 218 can be better accessed from above canopy 206, however, such raised positioning can create high moments and forces at the hinge points of the blade connected to pitch link assembly 204, for example, at the vertical hinge pin 220 (see FIG. 3). Such high moments can damage internal parts of the link assembly during adjustment and, therefore, the blade must be lifted or otherwise supported to alleviate the force at the hinge points. This technique can be cumbersome to practice and time consuming to complete. Alternatively, pitch link assembly 204 can be completely removed from helicopter 200 (after installing a pitch lock pin) so that it can be easily adjusted by itself. After adjustment, pitch link assembly 204 must be reinstalled on helicopter 200. Of course, this can add significant time to the adjustment procedure, particularly when several pitch link assemblies need adjustment and/or when many iterative adjustments are needed for a single pitch link assembly.
Accordingly, it is desirable to have a helicopter pitch link assembly that can be easily adjusted while installed on a helicopter having a protective canopy and/or a protective boot surrounding the pitch link assembly. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.